1. Field of the Invention
The present invention relates to a sliver-knit material and, more specifically, it relates to a sliver-knit material which causes less buckling fatigue or deformation during compression, and has improved shedding properties. The sliver-knit material of the invention is suitable, particularly, as a skin material for paint rollers. The present invention also relates to a sliver-knit material which does not cause boundary line failure during production of paint rollers, and which has excellent holdability (liquid absorbability) and paint releasability (coatability), particularly, to thick coatings, as well as to a paint roller composed of this sliver-knit material.
2. Description of the Background
Heretofore, pile materials include those-prepared by planting or weaving pile fibers into a woven or knitted substrate fabric, which is used in various applications such as floor coverings. However, the pile materials have the drawback of causing stress concentration for external loads and suffer from buckling fatigue or shedding of pile threads.
On the other hand, in the paint roller application, fabrics containing synthetic fibers or pure wools and sponges and having coatings are used. Among them, sliver-knit materials using synthetic fibers, which are less expensive, have been used generally.
However, in the sliver-knit material described above, not all pile threads are secured to the base threads. Rather, many fibers free from the base threads and entangling with each other (hereinafter referred to as sheds) are present. One known drawback is that the sheds are detached due to the viscosity of coatings during coating operation and adhered to the coated surface (this is referred to as “shedding”).
Accordingly, for preventing shedding from the sliver-knit material, an operation of coating and impregnating a resin on the bottom side of a base material thereby fixing pile threads held by base threads and, further, brushing the piled surface of the sliver-knit material for removing sheds as much as possible has been applied. However, the applicability of such an operation is extremely limited.
Japanese Unexamined Utility Model Publication No. Hei 2-4679 proposes a roller-shaped brush using a base material incorporated with at least 10% or more of low melting point composite fibers in order to prevent detachment of sheds and forming fused portions with the low melting point composite fibers by using a suction type heat treating machine.
However, the sheds can not be suppressed completely by merely mixing a small amount of the low melting point composite fibers. Suppression of sheds was substantially impossible unless the low melting point composite fibers were used in a great amount in view of the mechanism in the production of the sliver-knit material.
When the low melting point composite fibers are used in a large amount, an improvement can be obtained to some extent for the detachment of sheds. However, since the base material itself is hardened, it cannot be wound around the core of a roller. Even when it can be wound around, boundary lines are formed to cause roller marks on the coated surface, failing to obtain a paint roller of high commercial value.
In addition, since the base material itself is hardened, gaps are formed on the piled surface to give a serious problem that no uniform piled surface can be formed.
Actually, Japanese Unexamined Utility Model Publication No. Hei 2-4679 describes a manufacturing method involving the use of a suction type heat treatment machine. However, since a hot blow penetrates the piled surface, fusion with the low melting point composite fibers is caused remarkably as far as the pile surface, the surface is also hardened to leave the problem that the boundary lines become conspicuous during production of paint rollers as described above.
Furthermore, the brushing process during production of paint roller is configured for masking the boundary lines. However, the effect of the suppression of sheds is undetermined by the application of the mentioned above, which break down the fusion with the low melting point composite fibers.
On the other hand, Japanese Unexamined Patent Publication No. 2002-302863 proposes a fiber structure for use in a coating tool, containing from 30 to 100 mass % of heat fusible fibers and having a reticular fused layer and a bulky layer with an aim of improving the coatability of a low viscosity fluid typically represented by photo-catalyst coatings containing, for example, an anatase titanium dioxide grade.
However, while the fiber structure described above can suppress shedding, it is recognized that the structure lacks in the basic performance as a paint roller of sufficiently holding and releasing thick coatings. This is because crimps appear frequently to fibers used in the fiber structure (large number of crimps) and, accordingly, fused portions are formed excessively in the reticular fused layer to lack in the flexibility.
In recent years, in view of the consideration for the environment, solvent type coatings have been changed to environmentally-friendly coatings such as water borne coatings. Accordingly, the viscosity of the coatings has increased significantly. In the paint roller using the existent sliver-knit material, the shedding described above has a serious problem.
Further, since thick coatings have a quick-drying property, there is a problem that the coatings are cured in the structure in a paint roller of poor circulation of coating. Then, the fiber structure described above causes a problem that the coatings are cured in the reticular fused layer.
Accordingly, since the coatings can be held actually only in the bulky layer, the content of the coatings is small thereby limiting coatability.
As described above, in the paint roller made of the sliver-knit material, it is a problem to suppress shedding while keeping the basic performance of a paint roller of sufficiently holding and releasing thick coatings. However, a paint roller capable of satisfying such performance requirements simultaneously has not yet been provided.